At a glance:

Endpoint Vulnerability

sendBeacon requests lack an Origin header

Description

Security researcher Muneaki Nishimura reported that navigator.sendBeacon() does not follow the cross-origin resource sharing (CORS) specification. This results in the request from sendBeacon() lacking an origin header in violation of the W3C Beacon specification and not being treated as a CORS request. This allows for a potential Cross-site request forgery (XSRF) attack from malicious websites.